In order to predict the distribution of shrinkage porosity in steel ingot efficiently and accurately, a criterion R√L and a method to obtain its
threshold value were proposed. The criterion R√L was derived based on the solidification characteristics of steel ingot and pressure
gradient in the mushy zone, in which the physical properties, the thermal parameters, the structure of the mushy zone and the secondary
dendrite arm spacing were all taken into consideration. The threshold value of the criterion R√L was obtained with combination of
numerical simulation of ingot solidification and total solidification shrinkage rate. Prediction of the shrinkage porosity in a 5.5 ton ingot of
2Cr13 steel with criterion R√L>0.21 m・℃1/2・s
-3/2 agreed well with the results of experimental sectioning. Based on this criterion,
optimization of the ingot was carried out by decreasing the height-to-diameter ratio and increasing the taper, which successfully eliminated
the centreline porosity and further proved the applicability of this criterion.